Truing or dressing attachment for thread grinding discs



April 1955 K. H. SCHULTZE 2,705,946

TRUING OR DRESSING ATTACHMENT FOR THREAD GRINDING DISCS Filed lay 18, 1953 2 Sheets-Sheet 1 Inventor": Kurt jcHuL'rzE April 12, 1955 K. H. SCHULTZE TRUING OR DRESSING ATTACHMENT FOR THREAD GRINDING DISCS Filed llay 18, 1953 2 Sheets-Sheet 2 United States Patent TRUING 0R DRESSING ATTACHNIENT FOR THREAD GRIWDING DISCS Kurt H. Schultze, Berlin-Frohnau, Germany, assignor to Erna Lindner, born Pfeiifer, Berlin-Frolmau, Germany Application May 18, 1953, Serial No. 355,509

Claims priority, application Germany May 26, 1952 7 Claims. (Cl. 125-11) It is known that the flanks of thread produced by disclike tools are not right-lined neither in the axial cross section nor in the normal cross section but are curved more or less. The flanks deviate from the right line and more, the smaller the angle of the flank and the larger the pitch angle of the thread and the diameter of the disc-liketool (in the present case the grinding disc).

Further truing or dressing devices are known allowing to correct the grinding disc in such a manner that rightlined flanks may he obtained in the axial cross section. These devices are inserted between the centers of the lathe instead of the work piece, the diamond moving to and fro in the plane of axial cross section, forming the right flank line passing in the axial direction of the thread along the grinding disc, with the pitch of the thread to be ground.

With such device it is, however, impossible to obtain right-lined flanks of the work piece also in the normal cross section, i. e. in the course of the helical line, a fact of great importance especially if hob cutters are involved. The profile of such cutters must be, in a normal cross section, exactly right-lined corresponding to the profile of the respective rack for the purpose of producing an exact evolvent at the toothed wheel to be cut.

This disadvantage is avoided according to the invention by a truing or dressing device for thread grinding discs allowing to produce flanks right-lined selectively in the axial or the normal cross section of the thread to be cut.

According to the invention the lining device comprises a beating provided on a base plate (upper slide) adjustable around the horizontal middle diameter of the grinding disc to the pitch angle of the thread, and provided with a guide nut coaxial with the work piece and corresponding to the pitch of the thread, and a link or yoke tiltable around the axis of the work piece and guided by a mandrel in the guide nut, a diamond plunger or the like being supported by said link in such a way that its direction of movement may be adjusted to the flank angle of the thread profile and the plane of its movement may be adjusted so as to be parallel to the plane of the axis of the grinding spindle or to the plane of the work piece axis, the function of the plunger producing the profile in the axial cross section if the plane of the movement of the plunger is parallel to the plane of the axis of the grinding disc, and in the normal cross section if the plane of the movement of the plunger is parallel to the plane of the work piece axis.

Further details of the invention may be seen from the following specification of an embodiment illustrated in the accompanying drawing.

In the drawing an embodiment of the invention is shown by way of example, in which the truing apparatus is located at the place provided for accommodating the usual truing devices and not clamped between the centers of lathe instead of the work piece. Thereby the advantage results that the grinding disc may be re-sharpened, it required, without removing the work piece, even if the work piece is not yet finished. However, the device according to the invention may also be constructed so as to be clamped between the centers.

Fig. 1 is a vertical sectional view of the device, the section being taken in a plane across the axis of the grinding disc. For the sake of clearness, the device is shown without a pitch angle of the thread.

Fig. 2 is a plan view of Fig. 1.

Fig. 3 is a section taken in the plane of the line 3-3 2,705,945 Patented Apr. 12, 1955 in Fig. 1 and shows the device adjusted to the pitch angle a, i. e. adjusted for obtaining right-lined flanks in the normal cross section.

Fig. 4 shows the grinding disc engaging a work piece to be ground and positioned before the truing device, seen from the side of the worker, the grinding table of the thread grinding machine being adjusted to the pitch angle 0:.

Fig. 5 shows a section of the thread profile with rightlined flanks in the normal cross section, taken in the plane of the line II of Fig. 3.

In Figs. 1 to 3 of the drawings 1 designates the grinding disc to be dressed. The lower slide 2 is fixed on the place destined for the truing devices. Its base lies in a plane parallel to the plane of the horizontal axis I--I of the grinding spindle. The lower slide 2 guides the upper slide 3 adapted to be adjusted toward the grinding disc by means of the hand wheel 4, the spindle 5 and the nut 6. The upper slide 3 forms a base plate of the truing device; it has a segmental guiding surface 3 by which the bearing support 8 may be adjusted around the center 7 so as to be equal to the pitch angle of the thread to be ground. To the bearing support 8 a link or yoke 9 is pivoted. Its pivot 9 (Fig. 3) is adapted to receive the threaded mandrel 11 having the pitch of the thread to be ground. The associated guide nut 12 is fastened in the bearing support 8. At the opposite side the bearing support 8 carries a flanged casing 13 containing a pressure spring 14 and a pressure piece 15. The pressure spring prevents lost motion in the thread between the mandrel and the guide nut. The link or yoke 9 has a segmental guide 9" along which a segment 16 may also be adjusted around the axis 7. The segment 16 simultaneously forms the guide for a slide 17 carrying the casing 18 of the diamond plunger 19 rotatable around the axis llI-III (Fig. 1 and 2). The diamond plunger 19 carries the diamond 2t) and may be rotated by within a guide not shown in the drawing. This guide moves to and fro in the casing 18. It is driven by the motor 35 through the pinion 21 and the toothed gear 22 (Fig. 1). The casing 18 may be tilted towards opposite sides by the flank angle B or ,8 respectively (Fig. 2). The end positions are controlled by a stationary abutment 23 and the adjustable abutments 24 and 24 respectively. A clamping screw 25 fixes the casing 18 in its angular position required for the flank to be worked. Theplunger 19 may be turned around its axis by 180 by means of the handle 26 so that the diamond 20 is positioned as shown by dot and dash lines, such position of the diamond being required for truing or dressing the opposite flank of the grinding disc. The diamond 20 is provided with a fine adjustment device 27 by which the distance e of the axis IV-IV of the diamond plunger 19 from the grinding disc may be adjusted (Fig. 2). Besides, the diamond plunger 19 carries, at its front side, another diamond 29, serving for truing the outer diameter of the grinding disc and for adjusting the device to the measure R (Fig. 2).

If, e. g. the grinding disc is to be trued suchwise that the thread of the work piece 23 (Fig. 4) has a right-lined flank in the normal cross section, i. e. in a section taken in the plane comprising the line II and being perpendicularly to the helical line of the thread, corresponding to Fig. 5, first the mandrel 11 corresponding to the pitch of the thread to be ground and the guide nut 12 belonging thereto must be mounted, then the bearing support 8 is tilted so as to be at the pitch angle a and the segment 16 is adjusted so that the axis IVIV (Fig. 2) of the diamond plunger 19 may be positioned in a plane parallel to the axis lI of the grinding disc and the segment 16 has the position shown in Fig. 3. Then the casing 18 is adjusted to the flank angles ,8 and ,B' (Fig. 2) by means of the abutments 24 and 24. The diamond 20 is adjusted to the measure e by means of the fine adjustment device 27. Now, the bearing support 8 is adjusted to the measure R corresponding to the radius of core diameter of the thread to be ground. This adjustment is made in the following way: First, the diamond plunger 19 is brought into a position remotest from the grinding disc 1 by turning of the button 28 of the motor 35 (Fig. 1). Then, the casing 18 is turned into its middle position so that the diamond plunger axis IV-IV is directed toward the center of the grinding disc, i. e. the casing is adjusted to a flank angle of Now, the slide 17 is adjusted so as to remove the diamond 29 provided in the front face of the diamond plunger 19, from the axis 11-11 by the amount R. For this purpose the measuring surfaces 30 and 30' (Fig. 2) provided at the link 9 may be used which surfaces have a known constant measure. For performing this adjustment the link 9 is locked in the position shown in Fig. i by means of the index detent 31 (Fig. 3) provided at the bearing support 8. Then the outer diameter of the roughly preliminarily profiled grinding disc 1 is brought into engagement with the diamond 29 by adjustment of the hand wheel 4. After the screw 32 is loosened the outer profile edge of the grinding disc 1 may be trued by turning of the guide nut 12 by-means of the handle 33. Now, the apparatus has the correct distance R from the grinding disc.

The casing 18 is first adjusted to. the flank angle 5 and the guide nut 12 is turned so that the diamond may pass the flank of the grinding disc. After the motor 35 is started the diamond plunger 19 moves to and fro and the one flank is trued, the plunger being fed by a motor (not shown) and the guiding nut 12. The position of the guiding nut 12 may be seen from a scale provided at its collar. Then the casing 18 is adjusted to the flank angle 5', the diamond plunger 19 is switched over by the handle 26 and the apparatus is operated in the same manner as described before. The new position of the guide nut may also be read from the mentioned scale. Now, the diamond 20 is removed from the grinding disc by the fine adjustment device 27 and the guide nut is turned to half the difference of the amount read off so that the diamond plunger is now correctly adjusted.

For the purpose of correcting the preliminarily profiled grinding disc so as to produce the requested rightlined profile in the normal cross section, the following steps must be taken. First the index detent 31 is disengaged so that the link or yoke 9 may be tilted by means of the handle 34 around the axis II--II and the to and fro moving diamond 20 may produce a helical surface, said diamond being simultaneously displaced in the axial direction by the mandrel 11 and the guide nut 12. The produced helical surface is identical with the helical surface of the thread to be made and corrects the flanks in the required manner if it passes along the grinding disc. In this way first the one flank and then the other flank is trued. It is important to adjust the diamond 20 by the fine adjustment 27 suchwise that the correct width of gaps is obtained in the finished thread. This may be ascertained by test grinding of a thin steel sheet and measuring it by a measuring microscope.

If a thread is to be made having a right-lined profile in the axial cross section the segment 16 must be adjusted so that the axis IVIV of the diamond plunger lies in a plane parallel to the plane of the tilting axis II-II. The segment must, therefore, be tilted from the position shown in Fig. 3 by the angle at around the center 7. Besides, the operation is the same as before.

What I claim is:

l. A truing attachment for thread grinding discs comprising, in combination, a base plate, a bearing support attached to said base plate so as to be adjustable to the pitch angle of the thread, around the horizontal middle diameter of the grinding disc, a guiding nut attached to said bearing support so that the axis of the guiding nut coincides with the axis of the work piece, a yoke pivotally supported by said bearing support so as to be turnable around the last mentioned axis, a threaded mandrel provided on one of the pivots of said yoke and engaging said guiding nut, and a diamond plunger displaceably supported by said yoke so as to adjust the direction of movement of the said plunger to the flanks of the thread profile, so that the direction of movement of said plunger is in a plane being parallel to one of the axis of the grinding spindle and the work piece axis.

2. A truing attachment for thread grinding discs comprising, in combination, a base plate, a bearing support attached to said base plate so as to be adjustable to the pitch angle of the thread, around the horizontal middle diameter of the grinding disc, a guiding nut attached to said bearing support so that the axis of the guiding nut coincides with the axis of the work piece, a yoke pivotally supported by said bearing support so as to be turnable around the last mentioned axis, a threaded mandrel provided on one of the pivots of said yoke and engaging said guiding nut, a segment guided by said yoke so as to be tiltable around the horizontal middle diameter of the grinding disc, a slide movably arranged on said segment, and a diamond plunger provided with a casing arranged on said slide so that said plunger may be adjusted with respect to the direction of its movement and with respect to the plane of its movement.

3. A truing attachment for thread grinding discs as claimed in claim 1 in combination with a pressure spring acting in the direction of the tilting axis of said yoke and adapted to remove the lost motion between the said guiding nut and said mandrel.

4. A truing attaghment for thread grinding discs as claimed in claim 2, said diamond plunger being rotatable in its casing by 180.

References Cited in the file of this patent UNITED STATES PATENTS 2,188,016 Schicht Jan. 23, 1940 2,344,332 Turrettini Mar. 14, 1944 2,646,030 Davis July 21, 1953 FOREIGN PATENTS 610,369 Great Britain Oct. 14, 1948 

